The present invention relates to a manufacturing process for a pressure connecting terminal.
By folding a plate member so as to form a frame portion and forming a slot in that frame, a kind of pressure connecting terminal is created. This kind of pressure connecting terminal has been employed for several kinds of wiring. In this kind of pressure connecting terminal, a wire coated with insulation material is pressed downwards into the slot in a way that the insulating coat of the wire is partly cut and stripped. Accordingly, the stripped portion of the coated wire is electrically connected with the pressure connecting terminal.
The above-described type of pressure connecting terminal is shown as an example in FIGS. 1, and 2. This pressure connecting terminal has an extending connection part 3 on one side end of a base plate 1 and an electrical wire connection part 5 on the other side end of the base plate 1. The electrical wire connection part 5 has a box like shape. In the electrical wire connection part 5, pressure connecting parts 11, 13, which are two walls oppositely arranged in a longitudinal direction of the pressure connecting terminal, are provided with slots 7, 9, respectively. A coated wire is placed on the slots 7, 9, pressed downwards, and fitted in the slots 7, 9 so that the insulating coat of the wire is cut and stripped, thereby creating an electrical connection of the stripped wire with the pressure connecting parts 11, 13.
A piece of strip mill comprising a copper alloy is generally employed as a base material for the above-described type of pressure connecting terminal. Further, the piece of strip mill is plated with tin (Sn) in order to improve electrical connectability thereof. Namely, the piece of strip mill is tin plated in order to provide a reliable electrical connection between the electrical wire connection part 5 and a stripped portion of a wire coated with insulation material.
The following is an example of a manufacturing process for the above-mentioned type of pressure connecting terminal. First, a whole piece of strip mill is tin plated in advance. This piece of tin plated strip mill is then sliced so as to provide bars of strip mill each of whose width corresponds to a longitudinal width of the pressure connecting terminal itself. Flat blanks are then punch cut from the bars by means of press working in accordance with a predetermined pattern. Finally, after being folded into a predetermined shape of the pressure connecting terminal, the blank is tin plated a second time in order to form a layer of tin plating on punch cut edges which are newly created after press working, especially, on the edges of slots 7, 9.
In the second example for manufacturing the pressure connecting terminal, a piece of strip mill is sliced so as to provide bars of strip mill each of whose width corresponds to a width of the pressure connecting terminal itself. Blanks are cut from the bars by means of press working. Then, the blank is folded into a predetermined shape of the pressure connecting terminal. Finally, the whole body of the folded pressure connecting terminal is tin plated. Namely, in this example, the tin plating is executed only as a final step.
Inconveniently, the first example described above requires that tin plating be carried out twice, thereby resulting in a high manufacturing cost. Moreover, because the tin plating takes place twice, an unnecessary thickness of the tin layer on the pressure connecting terminal develops. In this way, when recycled, an inconvenient removing process for the thick tin layers may be required.
With regard to the latter example, the fact that tin plating occurs only one time may be convenient. However, since the tin plating is applied to the pressure connecting terminal which was previously formed into a particular shape, surface irregularities with respect to the tin plating may occur often, and, in a most unfortunate situation, tin plating of the slots 7, 9 does not succeed.